System and method for coordinated link up handling following switch reset in a high performance computing network

ABSTRACT

Systems and methods for supporting coordinated link up handling following a switch reset in a high performance computing environment. Systems and methods can ensure that when a switch of a fabric is rebooted, HCA ports connected to that switch will be set in Active state at the same time even though link training times for different ports may vary with up to several seconds.

CLAIM OF PRIORITY

This application claims the benefit of priority to U.S. ProvisionalApplication titled “SYSTEM AND METHOD FOR COORDINATED LINK UP HANDLINGFOLLOWING SWITCH RESET IN AN INFINIBAND NETWORK”, Application No.62/438,798, filed on Dec. 23, 2016.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

Field of Invention

The present invention is generally related to computer systems, and isparticularly related to supporting coordinated link up handlingfollowing switch reset in a network environment.

Background

As larger cloud computing architectures are introduced, the performanceand administrative bottlenecks associated with the traditional networkand storage have become a significant problem. There has been anincreased interest in using high performance lossless interconnects suchas InfiniBand (IB) technology as the foundation for a cloud computingfabric. This is the general area that embodiments of the invention areintended to address.

SUMMARY

Described herein are systems methods for supporting coordinated link uphandling following a switch reset in a high performance computingenvironment, such as an InfiniBand™ network, in accordance with anembodiment. Systems and methods can ensure that when a switch of afabric is rebooted, HCA ports connected to that switch can be set inActive state at the same time even though link training times fordifferent ports may vary with up to several seconds.

In accordance with an embodiment, an exemplary method for supportingcoordinated link up handling following a switch reset in a highperformance computing environment can provide, at the one or morecomputers, including one or more microprocessors a first subnet, thefirst subnet comprising a plurality of switches, the plurality ofswitches comprising at least a leaf switch, wherein each of theplurality of switches comprise a plurality of switch ports, a pluralityof host channel adapters, wherein each of the host channel adapterscomprise at least one virtual function, at least one virtual switch, andat least one physical function, and wherein the plurality of hostchannel adapters are interconnected via the plurality of switches, aplurality of hypervisors, wherein each of the plurality of hypervisorsare associated with at least one host channel adapter of the pluralityof host channel adapters, a plurality of virtual machines, wherein eachof the plurality of virtual machines are associated with at least onevirtual function, and a subnet manager, the subnet manager running onone of the plurality of switches and the plurality of host channeladapters. The method can reset a switch of the plurality of switches.Upon the reset of the switch of the plurality of switches, the methodcan associate the switch with a boot attribute, the boot attribute beingaccessible, via a subnet management packet, by at least the subnetmanager.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an illustration of an InfiniBand environment, in accordancewith an embodiment.

FIG. 2 shows an illustration of a partitioned cluster environment, inaccordance with an embodiment

FIG. 3 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment.

FIG. 4 shows an exemplary shared port architecture, in accordance withan embodiment.

FIG. 5 shows an exemplary vSwitch architecture, in accordance with anembodiment.

FIG. 6 shows an exemplary vPort architecture, in accordance with anembodiment.

FIG. 7 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment.

FIG. 8 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment.

FIG. 9 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.

FIG. 10 shows an exemplary multi-subnet InfiniBand fabric, in accordancewith an embodiment.

FIG. 11 shows an interconnection between two subnets in a highperformance computing environment, in accordance with an embodiment.

FIG. 12 shows an interconnection between two subnets via a dual-portvirtual router configuration in a high performance computingenvironment, in accordance with an embodiment.

FIG. 13 shows a flowchart of a method for supporting dual-port virtualrouter in a high performance computing environment, in accordance withan embodiment.

FIG. 14 illustrates a system for supporting coordinated link up handlingfollowing a switch reset in a high performance computing environment, inaccordance with an embodiment.

FIG. 15 illustrates a system for supporting coordinated link up handlingfollowing a switch reset in a high performance computing environment, inaccordance with an embodiment.

FIG. 16 is a flowchart of a method for supporting coordinated link uphandling following a switch reset in a high performance computingenvironment, in accordance with an embodiment.

DETAILED DESCRIPTION

The invention is illustrated, by way of example and not by way oflimitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” or “some” embodiment(s) in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone. While specific implementations are discussed, it is understood thatthe specific implementations are provided for illustrative purposesonly. A person skilled in the relevant art will recognize that othercomponents and configurations may be used without departing from thescope and spirit of the invention.

Common reference numerals can be used to indicate like elementsthroughout the drawings and detailed description; therefore, referencenumerals used in a figure may or may not be referenced in the detaileddescription specific to such figure if the element is describedelsewhere.

Described herein are systems and methods for supporting coordinated linkup handling following a switch reset in a high performance computingenvironment, in accordance with an embodiment.

The following description of the invention uses an InfiniBand™ (IB)network as an example for a high performance network. It will beapparent to those skilled in the art that other types of highperformance networks can be used without limitation. The followingdescription also uses the fat-tree topology as an example for a fabrictopology. It will be apparent to those skilled in the art that othertypes of fabric topologies can be used without limitation.

To meet the demands of the cloud in the current era (e.g., Exascaleera), it is desirable for virtual machines to be able to utilize lowoverhead network communication paradigms such as Remote Direct MemoryAccess (RDMA). RDMA bypasses the OS stack and communicates directly withthe hardware, thus, pass-through technology like Single-Root I/OVirtualization (SR-IOV) network adapters can be used. In accordance withan embodiment, a virtual switch (vSwitch) SR-IOV architecture can beprovided for applicability in high performance lossless interconnectionnetworks. As network reconfiguration time is critical to makelive-migration a practical option, in addition to network architecture,a scalable and topology-agnostic dynamic reconfiguration mechanism canbe provided.

In accordance with an embodiment, and furthermore, routing strategiesfor virtualized environments using vSwitches can be provided, and anefficient routing algorithm for network topologies (e.g., Fat-Treetopologies) can be provided. The dynamic reconfiguration mechanism canbe further tuned to minimize imposed overhead in Fat-Trees.

In accordance with an embodiment of the invention, virtualization can bebeneficial to efficient resource utilization and elastic resourceallocation in cloud computing. Live migration makes it possible tooptimize resource usage by moving virtual machines (VMs) betweenphysical servers in an application transparent manner. Thus,virtualization can enable consolidation, on-demand provisioning ofresources, and elasticity through live migration.

InfiniBand™

InfiniBand™ (IB) is an open standard lossless network technologydeveloped by the InfiniBand™ Trade Association. The technology is basedon a serial point-to-point full-duplex interconnect that offers highthroughput and low latency communication, geared particularly towardshigh-performance computing (HPC) applications and datacenters.

The InfiniBand™ Architecture (IBA) supports a two-layer topologicaldivision. At the lower layer, IB networks are referred to as subnets,where a subnet can include a set of hosts interconnected using switchesand point-to-point links. At the higher level, an IB fabric constitutesone or more subnets, which can be interconnected using routers.

Within a subnet, hosts can be connected using switches andpoint-to-point links. Additionally, there can be a master managemententity, the subnet manager (SM), which resides on a designated device inthe subnet. The subnet manager is responsible for configuring,activating and maintaining the IB subnet. Additionally, the subnetmanager (SM) can be responsible for performing routing tablecalculations in an IB fabric. Here, for example, the routing of the IBnetwork aims at proper load balancing between all source and destinationpairs in the local subnet.

Through the subnet management interface, the subnet manager exchangescontrol packets, which are referred to as subnet management packets(SMPs), with subnet management agents (SMAs). The subnet managementagents reside on every IB subnet device. By using SMPs, the subnetmanager is able to discover the fabric, configure end nodes andswitches, and receive notifications from SMAs.

In accordance with an embodiment, intra-subnet routing in an IB networkcan be based on LFTs stored in the switches. The LFTs are calculated bythe SM according to the routing mechanism in use. In a subnet, HostChannel Adapter (HCA) ports on the end nodes and switches are addressedusing local identifiers (LIDs). Each entry in an LFT consists of adestination LID (DLID) and an output port. Only one entry per LID in thetable is supported. When a packet arrives at a switch, its output portis determined by looking up the DLID in the forwarding table of theswitch. The routing is deterministic as packets take the same path inthe network between a given source-destination pair (LID pair).

Generally, all other subnet managers, excepting the master subnetmanager, act in standby mode for fault-tolerance. In a situation where amaster subnet manager fails, however, a new master subnet manager isnegotiated by the standby subnet managers. The master subnet manageralso performs periodic sweeps of the subnet to detect any topologychanges and reconfigure the network accordingly.

Furthermore, hosts and switches within a subnet can be addressed usinglocal identifiers (LIDs), and a single subnet can be limited to 49151unicast LIDs. Besides the LIDs, which are the local addresses that arevalid within a subnet, each IB device can have a 64-bit global uniqueidentifier (GUID). A GUID can be used to form a global identifier (GID),which is an IB layer three (L3) address.

The SM can calculate routing tables (i.e., the connections/routesbetween each pair of nodes within the subnet) at network initializationtime. Furthermore, the routing tables can be updated whenever thetopology changes, in order to ensure connectivity and optimalperformance. During normal operations, the SM can perform periodic lightsweeps of the network to check for topology changes. If a change isdiscovered during a light sweep or if a message (trap) signaling anetwork change is received by the SM, the SM can reconfigure the networkaccording to the discovered changes.

For example, the SM can reconfigure the network when the networktopology changes, such as when a link goes down, when a device is added,or when a link is removed. The reconfiguration steps can include thesteps performed during the network initialization. Furthermore, thereconfigurations can have a local scope that is limited to the subnets,in which the network changes occurred. Also, the segmenting of a largefabric with routers may limit the reconfiguration scope.

An example InfiniBand fabric is shown in FIG. 1, which shows anillustration of an InfiniBand environment 100, in accordance with anembodiment. In the example shown in FIG. 1, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. In accordance with an embodiment, the various nodes,e.g., nodes A-E, 101-105, can be represented by various physicaldevices. In accordance with an embodiment, the various nodes, e.g.,nodes A-E, 101-105, can be represented by various virtual devices, suchas virtual machines.

Partitioning in InfiniBand

In accordance with an embodiment, IB networks can support partitioningas a security mechanism to provide for isolation of logical groups ofsystems sharing a network fabric. Each HCA port on a node in the fabriccan be a member of one or more partitions. Partition memberships aremanaged by a centralized partition manager, which can be part of the SM.The SM can configure partition membership information on each port as atable of 16-bit partition keys (P_Keys). The SM can also configureswitch and router ports with the partition enforcement tables containingP_Key information associated with the end-nodes that send or receivedata traffic through these ports. Additionally, in a general case,partition membership of a switch port can represent a union of allmembership indirectly associated with LIDs routed via the port in anegress (towards the link) direction.

In accordance with an embodiment, partitions are logical groups of portssuch that the members of a group can only communicate to other membersof the same logical group. At host channel adapters (HCAs) and switches,packets can be filtered using the partition membership information toenforce isolation. Packets with invalid partitioning information can bedropped as soon as the packets reaches an incoming port. In partitionedIB systems, partitions can be used to create tenant clusters. Withpartition enforcement in place, a node cannot communicate with othernodes that belong to a different tenant cluster. In this way, thesecurity of the system can be guaranteed even in the presence ofcompromised or malicious tenant nodes.

In accordance with an embodiment, for the communication between nodes,Queue Pairs (QPs) and End-to-End contexts (EECs) can be assigned to aparticular partition, except for the management Queue Pairs (QP0 andQP1). The P_Key information can then be added to every IB transportpacket sent. When a packet arrives at an HCA port or a switch, its P_Keyvalue can be validated against a table configured by the SM. If aninvalid P_Key value is found, the packet is discarded immediately. Inthis way, communication is allowed only between ports sharing apartition.

An example of IB partitions is shown in FIG. 2, which shows anillustration of a partitioned cluster environment, in accordance with anembodiment. In the example shown in FIG. 2, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. The nodes A-E are arranged into partitions, namelypartition 1, 130, partition 2, 140, and partition 3, 150. Partition 1comprises node A 101 and node D 104. Partition 2 comprises node A 101,node B 102, and node C 103. Partition 3 comprises node C 103 and node E105. Because of the arrangement of the partitions, node D 104 and node E105 are not allowed to communicate as these nodes do not share apartition. Meanwhile, for example, node A 101 and node C 103 are allowedto communicate as these nodes are both members of partition 2, 140.

Virtual Machines in InfiniBand

During the last decade, the prospect of virtualized High PerformanceComputing (HPC) environments has improved considerably as CPU overheadhas been practically removed through hardware virtualization support;memory overhead has been significantly reduced by virtualizing theMemory Management Unit; storage overhead has been reduced by the use offast SAN storages or distributed networked file systems; and network I/Ooverhead has been reduced by the use of device passthrough techniqueslike Single Root Input/Output Virtualization (SR-IOV). It is nowpossible for clouds to accommodate virtual HPC (vHPC) clusters usinghigh performance interconnect solutions and deliver the necessaryperformance.

However, when coupled with lossless networks, such as InfiniBand (IB),certain cloud functionality, such as live migration of virtual machines(VMs), still remains an issue due to the complicated addressing androuting schemes used in these solutions. IB is an interconnectionnetwork technology offering high bandwidth and low latency, thus, isvery well suited for HPC and other communication intensive workloads.

The traditional approach for connecting IB devices to VMs is byutilizing SR-IOV with direct assignment. However, achieving livemigration of VMs assigned with IB Host Channel Adapters (HCAs) usingSR-IOV has proved to be challenging. Each IB connected node has threedifferent addresses: LID, GUID, and GID. When a live migration happens,one or more of these addresses change. Other nodes communicating withthe VM-in-migration can lose connectivity. When this happens, the lostconnection can be attempted to be renewed by locating the virtualmachine's new address to reconnect to by sending Subnet Administration(SA) path record queries to the IB Subnet Manager (SM).

IB uses three different types of addresses. A first type of address isthe 16 bits Local Identifier (LID). At least one unique LID is assignedto each HCA port and each switch by the SM. The LIDs are used to routetraffic within a subnet. Since the LID is 16 bits long, 65536 uniqueaddress combinations can be made, of which only 49151 (0x0001-0xBFFF)can be used as unicast addresses. Consequently, the number of availableunicast addresses defines the maximum size of an IB subnet. A secondtype of address is the 64 bits Global Unique Identifier (GUID) assignedby the manufacturer to each device (e.g. HCAs and switches) and each HCAport. The SM may assign additional subnet unique GUIDs to an HCA port,which is useful when SR-IOV is used. A third type of address is the 128bits Global Identifier (GID). The GID is a valid IPv6 unicast address,and at least one is assigned to each HCA port. The GID is formed bycombining a globally unique 64 bits prefix assigned by the fabricadministrator, and the GUID address of each HCA port.

Fat-Tree (FTree) Topologies and Routing

In accordance with an embodiment, some of the IB based HPC systemsemploy a fat-tree topology to take advantage of the useful propertiesfat-trees offer. These properties include full bisection-bandwidth andinherent fault-tolerance due to the availability of multiple pathsbetween each source destination pair. The initial idea behind fat-treeswas to employ fatter links between nodes, with more available bandwidth,as the tree moves towards the roots of the topology. The fatter linkscan help to avoid congestion in the upper-level switches and thebisection-bandwidth is maintained.

FIG. 3 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment. As shown in FIG. 3, oneor more end nodes 201-204 can be connected in a network fabric 200. Thenetwork fabric 200 can be based on a fat-tree topology, which includes aplurality of leaf switches 211-214, and multiple spine switches or rootswitches 231-234. Additionally, the network fabric 200 can include oneor more intermediate switches, such as switches 221-224.

Also as shown in FIG. 3, each of the end nodes 201-204 can be amulti-homed node, i.e., a single node that is connected to two or moreparts of the network fabric 200 through multiple ports. For example, thenode 201 can include the ports H1 and H2, the node 202 can include theports H3 and H4, the node 203 can include the ports H5 and H6, and thenode 204 can include the ports H7 and H8.

Additionally, each switch can have multiple switch ports. For example,the root switch 231 can have the switch ports 1-2, the root switch 232can have the switch ports 3-4, the root switch 233 can have the switchports 5-6, and the root switch 234 can have the switch ports 7-8.

In accordance with an embodiment, the fat-tree routing mechanism is oneof the most popular routing algorithm for IB based fat-tree topologies.The fat-tree routing mechanism is also implemented in the OFED (OpenFabric Enterprise Distribution—a standard software stack for buildingand deploying IB based applications) subnet manager, Open℠.

The fat-tree routing mechanism aims to generate LFTs that evenly spreadshortest-path routes across the links in the network fabric. Themechanism traverses the fabric in the indexing order and assigns targetLIDs of the end nodes, and thus the corresponding routes, to each switchport. For the end nodes connected to the same leaf switch, the indexingorder can depend on the switch port to which the end node is connected(i.e., port numbering sequence). For each port, the mechanism canmaintain a port usage counter, and can use this port usage counter toselect a least-used port each time a new route is added.

In accordance with an embodiment, in a partitioned subnet, nodes thatare not members of a common partition are not allowed to communicate.Practically, this means that some of the routes assigned by the fat-treerouting algorithm are not used for the user traffic. The problem ariseswhen the fat tree routing mechanism generates LFTs for those routes thesame way it does for the other functional paths. This behavior canresult in degraded balancing on the links, as nodes are routed in theorder of indexing. As routing can be performed oblivious to thepartitions, fat-tree routed subnets, in general, provide poor isolationamong partitions.

In accordance with an embodiment, a Fat-Tree is a hierarchical networktopology that can scale with the available network resources. Moreover,Fat-Trees are easy to build using commodity switches placed on differentlevels of the hierarchy. Different variations of Fat-Trees are commonlyavailable, including k-ary-n-trees, Extended Generalized Fat-Trees(XGFTs), Parallel Ports Generalized Fat-Trees (PGFTs) and Real LifeFat-Trees (RLFTs).

A k-ary-n-tree is an n level Fat-Tree with k^(n) end nodes and n·k^(n-1)switches, each with 2 k ports. Each switch has an equal number of up anddown connections in the tree. XGFT Fat-Tree extends k-ary-n-trees byallowing both different number of up and down connections for theswitches, and different number of connections at each level in the tree.The PGFT definition further broadens the XGFT topologies and permitsmultiple connections between switches. A large variety of topologies canbe defined using XGFTs and PGFTs. However, for practical purposes, RLFT,which is a restricted version of PGFT, is introduced to define Fat-Treescommonly found in today's HPC clusters. An RLFT uses the same port-countswitches at all levels in the Fat-Tree.

Input/Output (I/O) Virtualization

In accordance with an embodiment, I/O Virtualization (IOV) can provideavailability of I/O by allowing virtual machines (VMs) to access theunderlying physical resources. The combination of storage traffic andinter-server communication impose an increased load that may overwhelmthe I/O resources of a single server, leading to backlogs and idleprocessors as they are waiting for data. With the increase in number ofI/O requests, IOV can provide availability; and can improve performance,scalability and flexibility of the (virtualized) I/O resources to matchthe level of performance seen in modern CPU virtualization.

In accordance with an embodiment, IOV is desired as it can allow sharingof I/O resources and provide protected access to the resources from theVMs. IOV decouples a logical device, which is exposed to a VM, from itsphysical implementation. Currently, there can be different types of IOVtechnologies, such as emulation, paravirtualization, direct assignment(DA), and single root-I/O virtualization (SR-IOV).

In accordance with an embodiment, one type of IOV technology is softwareemulation. Software emulation can allow for a decoupledfront-end/back-end software architecture. The front-end can be a devicedriver placed in the VM, communicating with the back-end implemented bya hypervisor to provide I/O access. The physical device sharing ratio ishigh and live migrations of VMs are possible with just a fewmilliseconds of network downtime. However, software emulation introducesadditional, undesired computational overhead.

In accordance with an embodiment, another type of IOV technology isdirect device assignment. Direct device assignment involves a couplingof I/O devices to VMs, with no device sharing between VMs. Directassignment, or device passthrough, provides near to native performancewith minimum overhead. The physical device bypasses the hypervisor andis directly attached to the VM. However, a downside of such directdevice assignment is limited scalability, as there is no sharing amongvirtual machines—one physical network card is coupled with one VM.

In accordance with an embodiment, Single Root IOV (SR-IOV) can allow aphysical device to appear through hardware virtualization as multipleindependent lightweight instances of the same device. These instancescan be assigned to VMs as passthrough devices, and accessed as VirtualFunctions (VFs). The hypervisor accesses the device through a unique(per device), fully featured Physical Function (PF). SR-IOV eases thescalability issue of pure direct assignment. However, a problempresented by SR-IOV is that it can impair VM migration. Among these IOVtechnologies, SR-IOV can extend the PCI Express (PCIe) specificationwith the means to allow direct access to a single physical device frommultiple VMs while maintaining near to native performance. Thus, SR-IOVcan provide good performance and scalability.

SR-IOV allows a PCIe device to expose multiple virtual devices that canbe shared between multiple guests by allocating one virtual device toeach guest. Each SR-IOV device has at least one physical function (PF)and one or more associated virtual functions (VF). A PF is a normal PCIefunction controlled by the virtual machine monitor (VMM), or hypervisor,whereas a VF is a light-weight PCIe function. Each VF has its own baseaddress (BAR) and is assigned with a unique requester ID that enablesI/O memory management unit (IOMMU) to differentiate between the trafficstreams to/from different VFs. The IOMMU also apply memory and interrupttranslations between the PF and the VFs.

Unfortunately, however, direct device assignment techniques pose abarrier for cloud providers in situations where transparent livemigration of virtual machines is desired for data center optimization.The essence of live migration is that the memory contents of a VM arecopied to a remote hypervisor. Then the VM is paused at the sourcehypervisor, and the VM's operation is resumed at the destination. Whenusing software emulation methods, the network interfaces are virtual sotheir internal states are stored into the memory and get copied as well.Thus the downtime could be brought down to a few milliseconds.

However, migration becomes more difficult when direct device assignmenttechniques, such as SR-IOV, are used. In such situations, a completeinternal state of the network interface cannot be copied as it is tiedto the hardware. The SR-IOV VFs assigned to a VM are instead detached,the live migration will run, and a new VF will be attached at thedestination. In the case of InfiniBand and SR-IOV, this process canintroduce downtime in the order of seconds. Moreover, in an SR-IOVshared port model the addresses of the VM will change after themigration, causing additional overhead in the SM and a negative impacton the performance of the underlying network fabric.

InfiniBand SR-IOV Architecture—Shared Port

There can be different types of SR-IOV models, e.g. a shared port model,a virtual switch model, and a virtual port model.

FIG. 4 shows an exemplary shared port architecture, in accordance withan embodiment. As depicted in the figure, a host 300 (e.g., a hostchannel adapter) can interact with a hypervisor 310, which can assignthe various virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, when using a shared port architecture,such as that depicted in FIG. 4, the host, e.g., HCA, appears as asingle port in the network with a single shared LID and shared QueuePair (QP) space between the physical function 320 and the virtualfunctions 330, 350, 350. However, each function (i.e., physical functionand virtual functions) can have their own GID.

As shown in FIG. 4, in accordance with an embodiment, different GIDs canbe assigned to the virtual functions and the physical function, and thespecial queue pairs, QP0 and QP1 (i.e., special purpose queue pairs thatare used for InfiniBand management packets), are owned by the physicalfunction. These QPs are exposed to the VFs as well, but the VFs are notallowed to use QP0 (all SMPs coming from VFs towards QP0 are discarded),and QP1 can act as a proxy of the actual QP1 owned by the PF.

In accordance with an embodiment, the shared port architecture can allowfor highly scalable data centers that are not limited by the number ofVMs (which attach to the network by being assigned to the virtualfunctions), as the LID space is only consumed by physical machines andswitches in the network.

However, a shortcoming of the shared port architecture is the inabilityto provide transparent live migration, hindering the potential forflexible VM placement. As each LID is associated with a specifichypervisor, and shared among all VMs residing on the hypervisor, amigrating VM (i.e., a virtual machine migrating to a destinationhypervisor) has to have its LID changed to the LID of the destinationhypervisor. Furthermore, as a consequence of the restricted QP0 access,a subnet manager cannot run inside a VM.

InfiniBand SR-IOV Architecture Models—Virtual Switch (vSwitch)

FIG. 5 shows an exemplary vSwitch architecture, in accordance with anembodiment. As depicted in the figure, a host 400 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 430, 440, 450, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 410. A virtual switch 415 can also be handled by thehypervisor 401.

In accordance with an embodiment, in a vSwitch architecture each virtualfunction 430, 440, 450 is a complete virtual Host Channel Adapter(vHCA), meaning that the VM assigned to a VF is assigned a complete setof IB addresses (e.g., GID, GUID, LID) and a dedicated QP space in thehardware. For the rest of the network and the SM, the HCA 400 looks likea switch, via the virtual switch 415, with additional nodes connected toit. The hypervisor 410 can use the PF 420, and the VMs (attached to thevirtual functions) use the VFs.

In accordance with an embodiment, a vSwitch architecture providetransparent virtualization. However, because each virtual function isassigned a unique LID, the number of available LIDs gets consumedrapidly. As well, with many LID addresses in use (i.e., one each foreach physical function and each virtual function), more communicationpaths have to be computed by the SM and more Subnet Management Packets(SMPs) have to be sent to the switches in order to update their LFTs.For example, the computation of the communication paths might takeseveral minutes in large networks. Because LID space is limited to 49151unicast LIDs, and as each VM (via a VF), physical node, and switchoccupies one LID each, the number of physical nodes and switches in thenetwork limits the number of active VMs, and vice versa.

InfiniBand SR-IOV Architecture Models—Virtual Port (vPort)

FIG. 6 shows an exemplary vPort concept, in accordance with anembodiment. As depicted in the figure, a host 300 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, the vPort concept is loosely definedin order to give freedom of implementation to vendors (e.g. thedefinition does not rule that the implementation has to be SRIOVspecific), and a goal of the vPort is to standardize the way VMs arehandled in subnets. With the vPort concept, both SR-IOV Shared-Port-likeand vSwitch-like architectures or a combination of both, that can bemore scalable in both the space and performance domains, can be defined.A vPort supports optional LIDs, and unlike the Shared-Port, the SM isaware of all the vPorts available in a subnet even if a vPort is notusing a dedicated LID.

InfiniBand SR-IOV Architecture Models—vSwitch with Prepopulated LIDs

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs.

FIG. 7 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment. As depicted in the figure, a number ofswitches 501-504 can provide communication within the network switchedenvironment 600 (e.g., an IB subnet) between members of a fabric, suchas an InfiniBand fabric. The fabric can include a number of hardwaredevices, such as host channel adapters 510, 520, 530. Each of the hostchannel adapters 510, 520, 530, can in turn interact with a hypervisor511, 521, and 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each of thehost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 600.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs. Referring to FIG. 5, the LIDs are prepopulated to the variousphysical functions 513, 523, 533, as well as the virtual functions514-516, 524-526, 534-536 (even those virtual functions not currentlyassociated with an active virtual machine). For example, physicalfunction 513 is prepopulated with LID 1, while virtual function 1 534 isprepopulated with LID 10. The LIDs are prepopulated in an SR-IOVvSwitch-enabled subnet when the network is booted. Even when not all ofthe VFs are occupied by VMs in the network, the populated VFs areassigned with a LID as shown in FIG. 5.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, each hypervisor can consume one LID for itselfthrough the PF and one more LID for each additional VF. The sum of allthe VFs available in all hypervisors in an IB subnet, gives the maximumamount of VMs that are allowed to run in the subnet. For example, in anIB subnet with 16 virtual functions per hypervisor in the subnet, theneach hypervisor consumes 17 LIDs (one LID for each of the 16 virtualfunctions plus one LID for the physical function) in the subnet. In suchan IB subnet, the theoretical hypervisor limit for a single subnet isruled by the number of available unicast LIDs and is: 2891 (49151available LIDs divided by 17 LIDs per hypervisor), and the total numberof VMs (i.e., the limit) is 46256 (2891 hypervisors times 16 VFs perhypervisor). (In actuality, these numbers are actually smaller sinceeach switch, router, or dedicated SM node in the IB subnet consumes aLID as well). Note that the vSwitch does not need to occupy anadditional LID as it can share the LID with the PF

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, communication paths are computed for all the LIDs thefirst time the network is booted. When a new VM needs to be started thesystem does not have to add a new LID in the subnet, an action thatwould otherwise cause a complete reconfiguration of the network,including path recalculation, which is the most time consuming part.Instead, an available port for a VM is located (i.e., an availablevirtual function) in one of the hypervisors and the virtual machine isattached to the available virtual function.

In accordance with an embodiment, a vSwitch architecture withprepopulated LIDs also allows for the ability to calculate and usedifferent paths to reach different VMs hosted by the same hypervisor.Essentially, this allows for such subnets and networks to use a LID MaskControl (LMC) like feature to provide alternative paths towards onephysical machine, without being bound by the limitation of the LMC thatrequires the LIDs to be sequential. The freedom to use non-sequentialLIDs is particularly useful when a VM needs to be migrated and carry itsassociated LID to the destination.

In accordance with an embodiment, along with the benefits shown above ofa vSwitch architecture with prepopulated LIDs, certain considerationscan be taken into account. For example, because the LIDs areprepopulated in an SR-IOV vSwitch-enabled subnet when the network isbooted, the initial path computation (e.g., on boot-up) can take longerthan if the LIDs were not pre-populated.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment.

FIG. 8 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment. As depicted in the figure,a number of switches 501-504 can provide communication within thenetwork switched environment 700 (e.g., an IB subnet) between members ofa fabric, such as an InfiniBand fabric. The fabric can include a numberof hardware devices, such as host channel adapters 510, 520, 530. Eachof the host channel adapters 510, 520, 530, can in turn interact with ahypervisor 511, 521, 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each of thehost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 700.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment. Referring to FIG. 7, the LIDs are dynamically assigned tothe various physical functions 513, 523, 533, with physical function 513receiving LID 1, physical function 523 receiving LID 2, and physicalfunction 533 receiving LID 3. Those virtual functions that areassociated with an active virtual machine can also receive a dynamicallyassigned LID. For example, because virtual machine 1 550 is active andassociated with virtual function 1 514, virtual function 514 can beassigned LID 5. Likewise, virtual function 2 515, virtual function 3516, and virtual function 1 534 are each associated with an activevirtual function. Because of this, these virtual functions are assignedLIDs, with LID 7 being assigned to virtual function 2 515, LID 11 beingassigned to virtual function 3 516, and LID 9 being assigned to virtualfunction 1 534. Unlike vSwitch with prepopulated LIDs, those virtualfunctions not currently associated with an active virtual machine do notreceive a LID assignment.

In accordance with an embodiment, with the dynamic LID assignment, theinitial path computation can be substantially reduced. When the networkis booting for the first time and no VMs are present then a relativelysmall number of LIDs can be used for the initial path calculation andLFT distribution.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, when a new VM is created in a systemutilizing vSwitch with dynamic LID assignment, a free VM slot is foundin order to decide on which hypervisor to boot the newly added VM, and aunique non-used unicast LID is found as well. However, there are noknown paths in the network and the LFTs of the switches for handling thenewly added LID. Computing a new set of paths in order to handle thenewly added VM is not desirable in a dynamic environment where severalVMs may be booted every minute. In large IB subnets, computing a new setof routes can take several minutes, and this procedure would have torepeat each time a new VM is booted.

Advantageously, in accordance with an embodiment, because all the VFs ina hypervisor share the same uplink with the PF, there is no need tocompute a new set of routes. It is only needed to iterate through theLFTs of all the physical switches in the network, copy the forwardingport from the LID entry that belongs to the PF of the hypervisor—wherethe VM is created—to the newly added LID, and send a single SMP toupdate the corresponding LFT block of the particular switch. Thus thesystem and method avoids the need to compute a new set of routes.

In accordance with an embodiment, the LIDs assigned in the vSwitch withdynamic LID assignment architecture do not have to be sequential. Whencomparing the LIDs assigned on VMs on each hypervisor in vSwitch withprepopulated LIDs versus vSwitch with dynamic LID assignment, it isnotable that the LIDs assigned in the dynamic LID assignmentarchitecture are non-sequential, while those prepopulated in aresequential in nature. In the vSwitch dynamic LID assignmentarchitecture, when a new VM is created, the next available LID is usedthroughout the lifetime of the VM. Conversely, in a vSwitch withprepopulated LIDs, each VM inherits the LID that is already assigned tothe corresponding VF, and in a network without live migrations, VMsconsecutively attached to a given VF get the same LID.

In accordance with an embodiment, the vSwitch with dynamic LIDassignment architecture can resolve the drawbacks of the vSwitch withprepopulated LIDs architecture model at a cost of some additionalnetwork and runtime SM overhead. Each time a VM is created, the LFTs ofthe physical switches in the subnet are updated with the newly added LIDassociated with the created VM. One subnet management packet (SMP) perswitch is needed to be sent for this operation. The LMC-likefunctionality is also not available, because each VM is using the samepath as its host hypervisor. However, there is no limitation on thetotal amount of VFs present in all hypervisors, and the number of VFsmay exceed that of the unicast LID limit. Of course, not all of the VFsare allowed to be attached on active VMs simultaneously if this is thecase, but having more spare hypervisors and VFs adds flexibility fordisaster recovery and optimization of fragmented networks when operatingclose to the unicast LID limit.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment and Prepopulated LIDs

FIG. 9 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.As depicted in the figure, a number of switches 501-504 can providecommunication within the network switched environment 800 (e.g., an IBsubnet) between members of a fabric, such as an InfiniBand fabric. Thefabric can include a number of hardware devices, such as host channeladapters 510, 520, 530. Each of the host channel adapters 510, 520, 530,can in turn interact with a hypervisor 511, 521, and 531, respectively.Each hypervisor can, in turn, in conjunction with the host channeladapter it interacts with, setup and assign a number of virtualfunctions 514, 515, 516, 524, 525, 526, 534, 535, 536, to a number ofvirtual machines. For example, virtual machine 1 550 can be assigned bythe hypervisor 511 to virtual function 1 514. Hypervisor 511 canadditionally assign virtual machine 2 551 to virtual function 2 515.Hypervisor 521 can assign virtual machine 3 552 to virtual function 3526. Hypervisor 531 can, in turn, assign virtual machine 4 553 tovirtual function 2 535. The hypervisors can access the host channeladapters through a fully featured physical function 513, 523, 533, oneach of the host channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 800.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a hybrid vSwitch architecture withdynamic LID assignment and prepopulated LIDs. Referring to FIG. 7,hypervisor 511 can be arranged with vSwitch with prepopulated LIDsarchitecture, while hypervisor 521 can be arranged with vSwitch withprepopulated LIDs and dynamic LID assignment. Hypervisor 531 can bearranged with vSwitch with dynamic LID assignment. Thus, the physicalfunction 513 and virtual functions 514-516 have their LIDs prepopulated(i.e., even those virtual functions not attached to an active virtualmachine are assigned a LID). Physical function 523 and virtual function1 524 can have their LIDs prepopulated, while virtual function 2 and 3,525 and 526, have their LIDs dynamically assigned (i.e., virtualfunction 2 525 is available for dynamic LID assignment, and virtualfunction 3 526 has a LID of 11 dynamically assigned as virtual machine 3552 is attached). Finally, the functions (physical function and virtualfunctions) associated with hypervisor 3 531 can have their LIDsdynamically assigned. This results in virtual functions 1 and 3, 534 and536, are available for dynamic LID assignment, while virtual function 2535 has LID of 9 dynamically assigned as virtual machine 4 553 isattached there.

In accordance with an embodiment, such as that depicted in FIG. 8, whereboth vSwitch with prepopulated LIDs and vSwitch with dynamic LIDassignment are utilized (independently or in combination within anygiven hypervisor), the number of prepopulated LIDs per host channeladapter can be defined by a fabric administrator and can be in the rangeof 0 <=prepopulated VFs <=Total VFs (per host channel adapter), and theVFs available for dynamic LID assignment can be found by subtracting thenumber of prepopulated VFs from the total number of VFs (per hostchannel adapter).

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

InfiniBand—Inter-Subnet Communication (Fabric Manager)

In accordance with an embodiment, in addition to providing an InfiniBandfabric within a single subnet, embodiments of the current disclosure canalso provide for an InfiniBand fabric that spans two or more subnets.

FIG. 10 shows an exemplary multi-subnet InfiniBand fabric, in accordancewith an embodiment. As depicted in the figure, within subnet A 1000, anumber of switches 1001-1004 can provide communication within subnet A1000 (e.g., an IB subnet) between members of a fabric, such as anInfiniBand fabric. The fabric can include a number of hardware devices,such as, for example, channel adapter 1010. Host channel adapters 1010can in turn interact with a hypervisor 1011. The hypervisor can, inturn, in conjunction with the host channel adapter it interacts with,setup a number of virtual functions 1014. The hypervisor canadditionally assign virtual machines to each of the virtual functions,such as virtual machine 1 10105 being assigned to virtual function 11014. The hypervisor can access their associated host channel adaptersthrough a fully featured physical function, such as physical function1013, on each of the host channel adapters. Within subnet B 1040, anumber of switches 1021-1024 can provide communication within subnet b1040 (e.g., an IB subnet) between members of a fabric, such as anInfiniBand fabric. The fabric can include a number of hardware devices,such as, for example, channel adapter 1030. Host channel adapters 1030can in turn interact with a hypervisor 1031. The hypervisor can, inturn, in conjunction with the host channel adapter it interacts with,setup a number of virtual functions 1034. The hypervisor canadditionally assign virtual machines to each of the virtual functions,such as virtual machine 2 1035 being assigned to virtual function 21034. The hypervisor can access their associated host channel adaptersthrough a fully featured physical function, such as physical function1033, on each of the host channel adapters. It is noted that althoughonly one host channel adapter is shown within each subnet (i.e., subnetA and subnet B), it is to be understood that a plurality of host channeladapters, and their corresponding components, can be included withineach subnet.

In accordance with an embodiment, each of the host channel adapters canadditionally be associated with a virtual switch, such as virtual switch1012 and virtual switch 1032, and each HCA can be set up with adifferent architecture model, as discussed above. Although both subnetswithin FIG. 10 are shown as using a vSwitch with prepopulated LIDarchitecture model, this is not meant to imply that all such subnetconfigurations must follow a similar architecture model.

In accordance with an embodiment, at least one switch within each subnetcan be associated with a router, such as switch 1002 within subnet A1000 being associated with router 1005, and switch 1021 within subnet B1040 being associated with router 1006.

In accordance with an embodiment, at least one device (e.g., a switch, anode . . . etc.) can be associated with a fabric manager (not shown).The fabric manager can be used, for example, to discover inter-subnetfabric topology, created a fabric profile (e.g., a virtual machinefabric profile), build a virtual machine related database objects thatforms the basis for building a virtual machine fabric profile. Inaddition, the fabric manager can define legal inter-subnet connectivityin terms of which subnets are allowed to communicate via which routerports using which partition numbers.

In accordance with an embodiment, when traffic at an originating source,such as virtual machine 1 within subnet A, is addressed to a destinationat a different subnet, such as virtual machine 2 within subnet B, thetraffic can be addressed to the router within subnet A, i.e., router1005, which can then pass the traffic to subnet B via its link withrouter 1006.

Virtual Dual Port Router

In accordance with an embodiment, a dual port router abstraction canprovide a simple way for enabling subnet-to-subnet router functionalityto be defined based on a switch hardware implementation that has theability to do GRH (global route header) to LRH (local route header)conversion in addition to performing normal LRH based switching

In accordance with an embodiment, a virtual dual-port router canlogically be connected outside a corresponding switch port. This virtualdual-port router can provide an InfiniBand specification compliant viewto a standard management entity, such as a Subnet Manager.

In accordance with an embodiment, a dual-ported router model impliesthat different subnets can be connected in a way where each subnet fullycontrols the forwarding of packets as well as address mappings in theingress path to the subnet.

In accordance with an embodiment, in a situation involving anincorrectly connected fabric, the use of a virtual dual-port routerabstraction can also allow a management entity, such as a Subnet Managerand IB diagnostic software, to behave correctly in the presence ofun-intended physical connectivity to a remote subnet.

FIG. 11 shows an interconnection between two subnets in a highperformance computing environment, in accordance with an embodiment.Prior to configuration with a virtual dual port router, a switch 1120 insubnet A 1101 can be connected through a switch port 1121 of switch1120, via a physical connection 1110, to a switch 1130 in subnet B 1102,via a switch port 1131 of switch 1130. In such an embodiment, eachswitch port, 1121 and 1131, are acting both as switch ports and routerports.

In accordance with an embodiment, a problem with this configuration isthat a management entity, such as a subnet manager in an InfiniBandsubnet, cannot distinguish between a physical port that is both a switchport and a router port. In such a situation, SM can treat the switchport as having a router port connected to that switch port. But if theswitch port is connected to another subnet, via, for example, a physicallink, with another subnet manager, then the subnet manager can be ableto send a discovery message out on the physical link. However, such adiscovery message cannot be allowed at the other subnet.

FIG. 12 shows an interconnection between two subnets via a dual-portvirtual router configuration in a high performance computingenvironment, in accordance with an embodiment.

In accordance with an embodiment, after configuration, a dual-portvirtual router configuration can be provided such that a subnet managersees a proper end node, signifying an end of the subnet that the subnetmanager is responsible for.

In accordance with an embodiment, at a switch 1220 in subnetA 1201, aswitch port can be connected (i.e., logically connected) to a routerport 1211 in a virtual router 1210 via a virtual link 1223. The virtualrouter 1210 (e.g., a dual-port virtual router), which while shown asbeing external to the switch 1220 can, in embodiments, be logicallycontained within the switch 1220, can also comprise a second routerport, router port II 1212. In accordance with an embodiment, a physicallink 1203, which can have two ends, can connect the subnetA 1201 viafirst end of the physical link with subnet B 1202 via a second end ofthe physical link, via router port II 1212 and router port II 1231,contained in virtual router 1230 in subnet B 1202. Virtual router 1230can additionally comprise router port 1232, which can be connected(i.e., logically connected) to switch port 1241 on switch 1240 via avirtual ink 1233.

In accordance with an embodiment, a subnet manager (not shown) onsubnetA can detect router port 1211, on virtual router 1210 as an endpoint of the subnet that the subnet manager controls. The dual-portvirtual router abstraction can allow the subnet manager on subnet A wantto deal with subnet A in a usual manner (e.g., as defined per theInfiniBand specification). At the subnet management agent level, thedual-port virtual router abstraction can be provided such that the SMsees the normal switch port, and then at the SMA level, the abstractionthat there is another port connected to the switch port, and this portis a router port on a dual-port virtual router. In the local SM, aconventional fabric topology can continued to be used (the SM sees theport as a standard switch port in the topology), and thus the SM seesthe router port as an end port. Physical connection can be made betweentwo switch ports that are also configured as router ports in twodifferent subnets.

In accordance with an embodiment, the dual-port virtual router can alsoresolve the issue that a physical link could be mistakenly connect tosome other switch port in the same subnet, or to a switch port that wasnot intended to provide a connection to another subnet. Therefore wealso, the methods and systems described herein also provide arepresentation of what is on the outside of a subnet.

In accordance with an embodiment, within a subnet, such as subnet A, alocal SM determines a switch port, and then determines a router portconnected to that switch port (e.g., router port 1211 connected, via avirtual link 1223, to switch port 1221). Because the SM sees the routerport 1211 as the end of the subnet that the SM manages, the SM cannotsend discovery and/or management messages beyond this point (e.g., torouter port II 1212).

In accordance with an embodiment, the dual-port virtual router describedabove provides a benefit that the dual-port virtual router abstractionis entirely managed by a management entity (e.g., SM or SMA) within thesubnet that the dual-port virtual router belongs to. By allowingmanagement solely on a local side, a system does not have to provide anexternal, independent management entity. That is, each side of a subnetto subnet connection can be responsible for configuring its owndual-port virtual router.

In accordance with an embodiment, and additionally to the above, becauseeach subnet is responsible for managing the local dual-port virtualrouter abstraction, each subnet manager is then also responsible andretains control over all data traffic within the subnet, including datatraffic exiting the controlled subnet, and data traffic entering thesubnet from a remote subnet.

In accordance with an embodiment, in a situation where a packet, such asan SMP, is addressed to a remote destination (i.e., outside of the localsubnet) arrives local target port that is not configured via thedual-port virtual router described above, then the local port can returna message specifying that it is not a router port.

Many features of the present invention can be performed in, using, orwith the assistance of hardware, software, firmware, or combinationsthereof. Consequently, features of the present invention may beimplemented using a processing system (e.g., including one or moreprocessors).

FIG. 13 shows a method for supporting dual-port virtual router in a highperformance computing environment, in accordance with an embodiment. Atstep 1310, the method can provide at one or more computers, includingone or more microprocessors, a first subnet, the first subnet comprisingone or more switches, the one or more switches comprising at least aleaf switch, wherein each of the one or more switches comprise aplurality of switch ports, a plurality of host channel adapters, whereineach of the host channel adapters comprise at least one virtualfunction, at least one virtual switch, and at least one physicalfunction, and wherein the plurality of host channel adapters areinterconnected via the one or more switches, a plurality of hypervisors,wherein each of the plurality of hypervisors are associated with atleast one host channel adapter of the plurality of host channeladapters, a plurality of virtual machines, wherein each of the pluralityof virtual machines are associated with at least one virtual function,and a subnet manager, the subnet manager running on one of the one ormore switches and the plurality of host channel adapters.

At step 1320, the method can configure a switch port of the plurality ofswitch ports on a switch of the one or more switches as a router port.

At step 1330, the method can logically connect the switch portconfigured as the router port is to a virtual router, the virtual routercomprising at least two virtual router ports.

Coordinated Link Up Handling Following Switch Reset

In an embodiment, when a switch in a fabric undergoes a switchreset/reboot, for any number of reasons (e.g., scheduled reboot, newfirmware, updating software), problems can arise because different portson the switch can come back online at different times. There can be, insome situations, delays on the order of seconds between when a firstswitch port of the switch coming back online (i.e., active link status),and when a last switch port of the switch comes back online (i.e.,active link status). This can occur, for example, because link trainingon different switch ports of the same switch can require differentamounts of time when the link logic is trying to optimize the variousparameters. When different ports on a same switch come back up (i.e.,achieve active link status) at different times, this can lead toconfusion within the fabric.

For example, in a situation where a leaf switch, that has undergone aswitch reset, has two down-going ports connected to two HCAs, andseveral hosts via the two HCAs, achieve active link status prior to anyup-going ports (that would otherwise be connected to more switches athigher switch levels), then a local subnet manager would see the leafswitch as a fully contained subnet with only one switch level and wouldconsequently complete the initialization of the single switch basedsubnet. This can confuse the connection management logic of theconnected hosts since they will see the local HCA ports being connectedto two different subnets with two independent master subnet managersrather than a single subnet with a single subnet manager. This, in turn,can cause other problems, which can lead to delays in getting an entiresubnet/fabric back up to full functionality. The methods and systemsdescribed herein of coordinated link up handling following switch resetcan alleviate such situations and improve the efficiency of suchswitched networks by preventing undue delay that can occur after aswitch reset.

FIG. 14 shows a system for supporting coordinated link up handingfollowing switch reset, in accordance with an embodiment.

More specifically, FIG. 14 depicts a problem that can present itselfwhen link up handling is not coordinated following a switch reset.

In accordance with an embodiment, within a subnet 1400, a leaf switch1424 can be connected to two or more host channel adapters, 1401 and1402. These HCAs can provide connectivity to the subnet 1400 to aplurality of hosts (not shown) connected to the HCAs.

In accordance with an embodiment, the leaf switch 1424 can have recentlyundergone a switch reset (e.g., reboot after a software update). Afterundergoing switch reset, the ports of leaf switch 1424, shown as P1-P16(in actuality, a port can comprise a greater number or a lesser numberof ports—only 16 ports are shown on leaf switch 1424 for the sake ofsimplicity), are in the process of being brought back online (link up).In the depicted example, P2 can be a first switch port of leaf switch1424 to come back up online (i.e., train the links to HCAs 1401 and1402), while the remaining ports, P1, and P3-P16, are still undergoinglink up.

In accordance with an embodiment, when a subnet manager (e.g., a localsubnet manager) gathers information about leaf switch 1424 at thedepicted moment of time, the subnet manager can determine that switchport P2, within leaf switch 1424, and the connected HCA 1402 (and therespective host) comprise a fully contained subnet with a single switchlevel, and could begin calculating routes accordingly. However, within amatter of seconds, the remaining switch ports, P1, and P3-P16, can comeback up with active link status. At this point, the subnet manager willhave to re-start discovery, leading to delay in route allocation andcalculation.

In accordance with an embodiment, systems and methods can ensure thatwhen a leaf switch is rebooted, HCAs connected in redundant fashion to asingle IB subnet with one port connected to the leaf switch beingrebooted and another port to another leaf switch controlled by thecurrent master SM do not experience a case of two master SMs (i.e., onemaster SM associated with each HCA port) since this may confuse thechoice of active HCA port on each individual host/HCA. This can be thecase even if a local SM on the rebooted switch is operational whilelinks between the rebooted switch and other switches in the subnet havestill not completed link training whereas local switch-HCA links havecompleted training.

In accordance with an embodiment, systems and methods can ensure thatwhen a leaf switch is reset, all HCA ports connected to this leaf switchbecome operational at the same time (i.e., within an order of a fewfractions of a second), even if link training times for different localswitch-HCA, and switch-switch, links varies by up to several seconds.

In accordance with an embodiment, systems and methods can ensure thatwhen any switch in an operational subnet (e.g., an InfiniBand subnet) isreset, then there will only be a single subnet re-routing andre-configuration operation after all relevant links have completedtraining independently of whether the link training times for differentlinks varies by up to several seconds.

FIG. 15 illustrates a system for supporting coordinated link up handlingfollowing a switch reset in a high performance computing environment, inaccordance with an embodiment.

In accordance with an embodiment, within a subnet 1500, a number of hostchannel adapters 1501 and 1502, can be interconnected via a number ofswitches, such as switches 1520-1525. The host channel adapters canprovide connectivity to the subnet to one or more hosts (not shown),wherein the hosts can comprise virtual hosts (e.g., virtual machinesutilizing a SR-IOV architecture), physical hosts, or a combination ofboth physical and virtual hosts. As well, the subnet can host one ormore routers, such as router 1526, which can provide interconnectionwith neighboring subnets, as described in more detail above. Suchneighboring subnets can comprise a number of switches, hosts, routers,and remote subnet managers.

In accordance with an embodiment, each switch within the subnet can beassociated with an attribute, such as a boot attribute. In the depictedembodiment, leaf switch 1525, has recently undergone a switchreset/reboot, and as such, it is currently associated (e.g., at the SMAor firmware of the switch) with boot attribute 1510 (e.g.,“BootInProgress”). Additionally, a subnet manager 1550, as describedabove, can be hosted at a node within the subnet 1500. For the sake ofconvenience, the subnet manager 1550 is not shown as being hosted by anyof the displayed nodes in the subnet. However, one of skill in the artshould understand that the subnet manager 1550 is hosted on a node ofthe subnet, as described above.

In addition, although not shown, the subnet 1500 can be interconnectedwith additional other subnets, each of which can also support a SMAattribute/abstraction at router ports for inter-subnet exchange ofmanagement information.

In accordance with an embodiment, the boot attribute 1510 can comprise anumber of different attributes. For the sake of convenience, only oneblock for the attribute is shown in the figure, but it is to beunderstood that the boot attribute block 1510 can comprise one or manyattributes.

In accordance with an embodiment, firmware controlling leaf switch 1525can reflect a “boot in progress” status attribute at the boot attribute1510. This attribute can be queried both by the SM 1550 as well as anysubnet manager hosted on leaf switch 1525 (not shown). This state can bepresent as long as not all enabled local links (i.e., links connected toleaf switch 1525) have trained (i.e., not all ports expected to beactive on leaf switch 1525 have completed training), or a maximum timefor waiting for link training has been reached (i.e., a configurabletimeout period). In such situations, a SM (local or remote) can detectthe “boot in progress” state for switches in the subnet detected throughdiscovery. As long as a discovered switch is in a boot in progressstate, as reflected by the boot attribute, the switch can be ignored bya SM (local or remote, relative to the switch being rebooted) for atleast the purposes of further discovery and may not be included in acurrent subnet topology.

In accordance with an embodiment, following initial discovery of aswitch in “boot in progress” state, detection of change (reset) of thisstate can take place as the result of periodic sweeps (e.g., a sweepinterval can be 10 seconds). Once the “boot in progress” state has beenreset, normal discovery of the switch and associated connectivity cantake place as normal. Since this happens only when all enabled linkshave trained, all HCA ports connected to this switch will be discoveredand brought to active state during the same discovery/initiationsequence from the master SM (i.e., the link discovery for all activelinks on the switch happen at approximately the same time). In the caseof a local SM, the same scheme will allow the local SM to start up asnormal, so that it will be ready to negotiate with a remote master SMonce the local “boot in progress” state has ended. In this way, therewill never be a period where there is a “local master” SM because linksto other switches have not yet trained.

In accordance with an embodiment, in order to minimize the risk of theboot process timing out and exiting the “boot in progress” state whensome links are still in the process of training, the configurabletimeout value can be set to a value that is significant relative to anassumed “long time” scenario for link training. That is, for worse casevalues for link training of 30-40 seconds, a timeout value can be setfor 50-60 seconds.

In accordance with an embodiment, since the SM in the worst case will bewaiting a full sweep period (e.g., 10 seconds) before observing that the“boot in progress” state has been reset, the total time before therebooting switch is discovered could be increased by 10-30 seconds.

accordance with an embodiment, from the perspective of a host, thisscheme will imply that the duration in which the local HCA port statestays in “Init” may be significant relative to what is normallyobserved. For example, if the link trains in the order of 10-20 seconds,then there could be in the order of up to more than a minute that thelink will just stay in Init state before the master SM is ready to bringit to Active state.

In accordance with an embodiment, in systems and methods where vendorspecific attributes are supported at the nodes (see, e.g., U.S. patentapplication Ser. No. 15/412,985, entitled “SYSTEM AND METHOD FORSUPPORTING FLEXIBLE FRAMEWORK FOR EXTENDABLE SMA ATTRIBUTES IN A HIGHPERFORMANCE COMPUTING ENVIRONMENT”, filed on Jan. 23, 2017, which isherein incorporated by reference) there are a few improvements that canbe made when: a) a switch chip is an independent reset/reboot domain,meaning that Reboot of the SCP (“embedded management server”) does notimply reset/reboot of any local switches; b) a switch firmware controlsaspects of link enabling and training independently of the SCP’; c) theswitch SMA is fully controlled by switch firmware and can support vendorspecific attributes; and d) both local and remote SMs observe the stateof both the main board switch (as well as any module based switches) viaIB link(s).

In accordance with an embodiment, during a booting process, a local SMAcan keep track of a “boot in progress state” that is reflected as astatus attribute that can be observed by any SM (i.e., local or remote)via SMP access as long as any local link is still in the process oftraining.

In accordance with an embodiment, a timeout period can be provided. Thetimeout period can be for how long the “boot in progress state” can lastduring a normal reboot. The timeout period can, in an embodiment, be inthe order of 50% longer than the worst case expected link training timefor any type of link currently supported. The timeout period can be setby a system administrator. The timeout period can also be calculatedbased upon a worst case expected link training time for any linkcurrently supported by a switch.

In accordance with an embodiment, a port with a link that is expected totrain can be “waited for”. As long as low level status info can tellthat a link is not connected, or the remote side is not operational,then this link should not be considered by the “wait” logic.

In accordance with an embodiment, links that correspond to portsrepresented by the switch SMA instances can be considered by the “bootin progress state” handling. For example, when virtual router ports aredefined, then the relevant physical link from the corresponding switchport will not be considered whereas the virtual link between the switchport and the virtual router port will always have physical state “up”.

In accordance with an embodiment, a vendor specific attribute can bedefined, such as “BootInProgressStatus.” The vendor specific attributecapability mask can define if this new attribute is supported. As longas the relevant capability is not supported then the SM will discoverthe switch and associated connectivity as normal. An SM will not useNodeDescription value for detecting “boot in progress” status for nodeswith a specific vendor ID. The SM can use NodeDescription value fordetecting “boot in progress” status for switch nodes that do not havevendor specific ID.

In accordance with an embodiment, the vendor specific attribute (i.e.,“BootInProgressStatus”) can have the following components:

-   -   BootInProgressFlag—this can be a Boolean value that reflects a        “number of ports currently waited for is non-zero, but it is up        to the implementation to decide if other local state will        contribute to still being in “boot in progress” state.    -   The number of ports currently waited for (i.e., where links are        still expected to train)    -   The number of ports that have been given up to wait for (i.e.,        failed to train)    -   The wait timeout value in milliseconds    -   The remaining max wait time in milliseconds    -   The total wait time so far    -   The “total wait time so far” will normally be the timeout value        minus the remaining time. However, in the exception case below,        this time may be longer.

In accordance with an embodiment, while the “boot in progress” status isactive, the switch instance may (in principle) accept both in-band andout-of-band requests to enable or disable a physical link. If apreviously disabled link is enabled, then the wait timeout can be reset,and this can be reflected by the relevant time value components

In accordance with an embodiment, any SM that “probes” the switchinstance via any operational port can use the “BootInProgressFlag”component as the boolean status defining if further discovery of thisswitch and inclusion in the subnet topology should take place at thistime.

In accordance with an embodiment, other components can be used forinformational purposes and can also be used to monitor progress. The SMinstance can determine if lack of progress within an SM defined periodwill cause the SM to report a problem. However, the SM should notinitiate any further discovery of the switch connectivity as long as theswitch is still reporting “boot in progress” status.

FIG. 16 is a flow chart of a method for supporting coordinated link uphandling following a switch reset in a high performance computingenvironment, in accordance with an embodiment.

At step 1610, the method can provide, at the one or more computers,including one or more microprocessors a first subnet, the first subnetcomprising a plurality of switches, the plurality of switches comprisingat least a leaf switch, wherein each of the plurality of switchescomprise a plurality of switch ports, a plurality of host channeladapters, wherein each of the host channel adapters comprise at leastone virtual function, at least one virtual switch, and at least onephysical function, and wherein the plurality of host channel adaptersare interconnected via the plurality of switches, a plurality ofhypervisors, wherein each of the plurality of hypervisors are associatedwith at least one host channel adapter of the plurality of host channeladapters, a plurality of virtual machines, wherein each of the pluralityof virtual machines are associated with at least one virtual function,and a subnet manager, the subnet manager running on one of the pluralityof switches and the plurality of host channel adapters.

At 1620, the method can reset a switch of the plurality of switches.

At 1630, upon the reset of the switch of the plurality of switches, themethod can associate the switch with a boot attribute, the bootattribute being accessible, via a subnet management packet, by at leastthe subnet manager.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample, and not limitation. The embodiments were chosen and describedin order to explain the principles of the invention and its practicalapplication. The embodiments illustrate systems and methods in which thepresent invention is utilized to improve the performance of the systemsand methods by providing new and/or improved features and/or providingbenefits such as reduced resource utilization, increased capacity,improved efficiency, and reduced latency.

In some embodiments, features of the present invention are implemented,in whole or in part, in a computer including a processor, a storagemedium such as a memory and a network card for communicating with othercomputers. In some embodiments, features of the invention areimplemented in a distributed computing environment in which one or moreclusters of computers is connected by a network such as a Local AreaNetwork (LAN), switch fabric network (e.g. InfiniBand), or Wide AreaNetwork (WAN). The distributed computing environment can have allcomputers at a single location or have clusters of computers atdifferent remote geographic locations connected by a WAN.

In some embodiments, features of the present invention are implemented,in whole or in part, in the cloud as part of, or as a service of, acloud computing system based on shared, elastic resources delivered tousers in a self-service, metered manner using Web technologies. Thereare five characteristics of the cloud (as defined by the NationalInstitute of Standards and Technology: on-demand self-service; broadnetwork access; resource pooling; rapid elasticity; and measuredservice. See, e.g. “The NIST Definition of Cloud Computing”, SpecialPublication 800-145 (2011) which is incorporated herein by reference.Cloud deployment models include: Public, Private, and Hybrid. Cloudservice models include Software as a Service (SaaS), Platform as aService (PaaS), Database as a Service (DBaaS), and Infrastructure as aService (IaaS). As used herein, the cloud is the combination ofhardware, software, network, and web technologies which delivers sharedelastic resources to users in a self-service, metered manner. Unlessotherwise specified the cloud, as used herein, encompasses public cloud,private cloud, and hybrid cloud embodiments, and all cloud deploymentmodels including, but not limited to, cloud SaaS, cloud DBaaS, cloudPaaS, and cloud IaaS.

In some embodiments, features of the present invention are implementedusing, or with the assistance of hardware, software, firmware, orcombinations thereof. In some embodiments, features of the presentinvention are implemented using a processor configured or programmed toexecute one or more functions of the present invention. The processor isin some embodiments a single or multi-chip processor, a digital signalprocessor (DSP), a system on a chip (SOC), an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA) orother programmable logic device, state machine, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. In someimplementations, features of the present invention may be implemented bycircuitry that is specific to a given function. In otherimplementations, the features may implemented in a processor configuredto perform particular functions using instructions stored e.g. on acomputer readable storage media.

In some embodiments, features of the present invention are incorporatedin software and/or firmware for controlling the hardware of a processingand/or networking system, and for enabling a processor and/or network tointeract with other systems utilizing the features of the presentinvention. Such software or firmware may include, but is not limited to,application code, device drivers, operating systems, virtual machines,hypervisors, application programming interfaces, programming languages,and execution environments/containers. Appropriate software coding canreadily be prepared by skilled programmers based on the teachings of thepresent disclosure, as will be apparent to those skilled in the softwareart.

In some embodiments, the present invention includes a computer programproduct which is a storage medium or computer-readable medium (media)having instructions stored thereon/in, which instructions can be used toprogram or otherwise configure a system such as a computer to performany of the processes or functions of the present invention. The storagemedium or computer readable medium can include, but is not limited to,any type of disk including floppy disks, optical discs, DVD, CD-ROMs,microdrive, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs,DRAMs, VRAMs, flash memory devices, magnetic or optical cards,nanosystems (including molecular memory ICs), or any type of media ordevice suitable for storing instructions and/or data. In particularembodiments, the storage medium or computer readable medium is anon-transitory storage medium or non-transitory computer readablemedium.

The foregoing description is not intended to be exhaustive or to limitthe invention to the precise forms disclosed. Additionally, whereembodiments of the present invention have been described using aparticular series of transactions and steps, it should be apparent tothose skilled in the art that the scope of the present invention is notlimited to the described series of transactions and steps. Further,where embodiments of the present invention have been described using aparticular combination of hardware and software, it should be recognizedthat other combinations of hardware and software are also within thescope of the present invention. Further, while the various embodimentsdescribe particular combinations of features of the invention it shouldbe understood that different combinations of the features will beapparent to persons skilled in the relevant art as within the scope ofthe invention such that features of one embodiment may incorporated intoanother embodiment. Moreover, it will be apparent to persons skilled inthe relevant art that various additions, subtractions, deletions,variations, and other modifications and changes in form, detail,implementation and application can be made therein without departingfrom the spirit and scope of the invention. It is intended that thebroader spirit and scope of the invention be defined by the followingclaims and their equivalents.

What is claimed is:
 1. A system for supporting coordinated link uphandling following a switch reset in a high performance computingenvironment, comprising: one or more microprocessors; a first subnet,the first subnet comprising a plurality of switches, the plurality ofswitches comprising at least a leaf switch, wherein each of theplurality of switches comprise a plurality of switch ports, a pluralityof host channel adapters, wherein each of the host channel adapterscomprise at least one virtual function, at least one virtual switch, andat least one physical function, and wherein the plurality of hostchannel adapters are interconnected via the plurality of switches, aplurality of hypervisors, wherein each of the plurality of hypervisorsare associated with at least one host channel adapter of the pluralityof host channel adapters, a plurality of virtual machines, wherein eachof the plurality of virtual machines are associated with at least onevirtual function, and a subnet manager, the subnet manager running onone of the plurality of switches and the plurality of host channeladapters; wherein a switch of the plurality of switches is reset; andwherein, upon the reset of the switch of the plurality of switches, theswitch is associated with a boot attribute, the boot attribute beingaccessible, via a subnet management packet, by at least the subnetmanager.
 2. The system of claim 1, wherein upon accessing the bootattribute, the subnet manager can query whether all ports of the switchhave completed training following the reset of the switch.
 3. The systemof claim 2, wherein upon accessing the boot attribute, the subnetmanager can query whether a number of ports of the switch are stillwaiting to train following the reset of the switch.
 4. The system ofclaim 1, wherein upon a timeout period lapsing following the associationof the reset switch with the boot attribute, the boot attribute iscleared.
 5. The system of claim 4, wherein the timeout period is set bya system administrator.
 6. The system of claim 4, wherein the timeoutperiod calculated based upon a worst case link training time, thetimeout period being calculated to be fifty percent more than the worstcase link training time.
 7. The system of claim 1, wherein the bootattribute is expressed as a subnet management agent (SMA) attribute. 8.A method for supporting coordinated link up handling following a switchreset in a high performance computing environment, comprising:providing, at one or more computers, including one or moremicroprocessors a first subnet, the first subnet comprising a pluralityof switches, the plurality of switches comprising at least a leafswitch, wherein each of the plurality of switches comprise a pluralityof switch ports, a plurality of host channel adapters, wherein each ofthe host channel adapters comprise at least one virtual function, atleast one virtual switch, and at least one physical function, andwherein the plurality of host channel adapters are interconnected viathe plurality of switches, a plurality of hypervisors, wherein each ofthe plurality of hypervisors are associated with at least one hostchannel adapter of the plurality of host channel adapters, a pluralityof virtual machines, wherein each of the plurality of virtual machinesare associated with at least one virtual function, and a subnet manager,the subnet manager running on one of the plurality of switches and theplurality of host channel adapters; resetting a switch of the pluralityof switches; and upon the reset of the switch of the plurality ofswitches, associating the switch with a boot attribute, the bootattribute being accessible, via a subnet management packet, by at leastthe subnet manager.
 9. The method of claim 8, wherein upon accessing theboot attribute, the subnet manager can query whether all ports of theswitch have trained following the reset of the switch.
 10. The method ofclaim 9, wherein upon accessing the boot attribute, the subnet managercan query whether a number of ports of the switch are still waiting totrain following the reset of the switch.
 11. The method of claim 8,wherein upon a timeout period lapsing following the association of thereset switch with the boot attribute, the boot attribute is cleared. 12.The method of claim 11, wherein the timeout period is set by a systemadministrator.
 13. The method of claim 11, wherein the timeout periodcalculated based upon a worst case link training time, the timeoutperiod being calculated to be fifty percent more than the worst caselink training time.
 14. The method of claim 8, wherein the bootattribute is expressed as a subnet management agent (SMA) attribute. 15.A non-transitory computer readable storage medium having instructionsthereon for supporting coordinated link up handling following a switchreset in a high performance computing environment, which when read andexecuted by one or more computers cause the one or more computers toperform the steps comprising: providing, at the one or more computers,including one or more microprocessors a first subnet, the first subnetcomprising a plurality of switches, the plurality of switches comprisingat least a leaf switch, wherein each of the plurality of switchescomprise a plurality of switch ports, a plurality of host channeladapters, wherein each of the host channel adapters comprise at leastone virtual function, at least one virtual switch, and at least onephysical function, and wherein the plurality of host channel adaptersare interconnected via the plurality of switches, a plurality ofhypervisors, wherein each of the plurality of hypervisors are associatedwith at least one host channel adapter of the plurality of host channeladapters, a plurality of virtual machines, wherein each of the pluralityof virtual machines are associated with at least one virtual function,and a subnet manager, the subnet manager running on one of the pluralityof switches and the plurality of host channel adapters; resetting aswitch of the plurality of switches; and upon the reset of the switch ofthe plurality of switches, associating the switch with a boot attribute,the boot attribute being accessible, via a subnet management packet, byat least the subnet manager.
 16. The non-transitory computer readablestorage medium of claim 15, wherein upon accessing the boot attribute,the subnet manager can query whether all ports of the switch havecompleted training following the reset of the switch.
 17. Thenon-transitory computer readable storage medium of claim 16, whereinupon accessing the boot attribute, the subnet manager can query whethera number of ports of the switch are still waiting to train following thereset of the switch.
 18. The non-transitory computer readable storagemedium of claim 15, wherein upon a timeout period lapsing following theassociation of the reset switch with the boot attribute, the bootattribute is cleared.
 19. The non-transitory computer readable storagemedium of claim 18, wherein the timeout period is set by a systemadministrator.
 20. The non-transitory computer readable storage mediumof claim 15, wherein the boot attribute is expressed as a subnetmanagement agent (SMA) attribute.